1. Field of the Invention
This invention relates to apparatus and process for making caseless (skinless) sausage. In particular, this invention relates to a particular reusable tubular casing and associated apparatus for making parboil or raw sausage.
2. Description of the Prior Art
In general, the art recognized three types of sausages: cooking sausage, parboil sausage, and raw sausage. Cooking sausage has a higher fat and protein content and accordingly contains a smaller amount of water than the parboil sausage. For this reason cooking sausage releases practically no water during the heating process, and can therefore be produced in casings that are impenetrable by water vapor and steam evolved during the sausage-making process. For example, many organic polymeric materials that are impervious to water and steam, can be used with cooking sausage.
On the other, a larger amount of water is released during reddening and coagulation of the parboil sausage, and during the reddening and ripening process for raw sausage.
Parboil sausage is produced from an emulsion in water of a protein and fat. During the formation of this emulsion in high capacity grinding or cutting machines, ice is used for cooling. For this reason, the bulk sausage contains more water than is permissible for the perservation, of the sausage. Therefore, the bulk sausage must release about 5 to 50% (as an average about 10% ) gaseous constituents, in relation to the raw (unprocessed sausage meat) weight. These gaseous constituents consist for the most part of water vapor or steam, but also contain aromatic constituents and other volatile substances released during the heating steps for reddening and/or coagulation.
The reddening of parboil sausage occurs as a rule at about 35.degree. C. within approximately 15 minutes; the coagulation must be carried out at temperatures above 45.degree. C. and takes place as a rule by heating in water or steam at temperatures between 70.degree. and 100.degree. C., usually at about 80.degree. C., in a relatively short time.
Almost all parboil sausages are smoked. It is a general practice to complete the smoking process after reddening, but before coagulation. Since the sausage casings in use at the present time have little permeability for smoke, the smoking process normally takes a long time.
Raw sausage is produced from bulk sausage which contains fat and meat pieces of various size. During the reddening and ripening process the bulk sausages releases gasous constitutents from about 10 to 50%, as related to the raw (unprocessed bulk) weight. These gaseous constituents also consist for the most part of water vapor, however, they also contain aromatic constituents and substances volatile under the conditions of the reddening and/or ripening process.
The reddening and ripening of raw sausage occurs at temperatures not above 40.degree. C., as a rule at around 20.degree. C. The reddening and ripening occurs quite slowly during the course of a few days up to several months. Some types of raw sausages are also smoked. In the reddening and ripening process for others, as for instance salami, mildew (mold) is expected to form.
In original sausage making procedures, the bulk sausage was injected into a natural intestine and subsequently subjected to the treatment required by a particular type of sausage. Artificial intestines made of various materials have been known for quite some time. Most of the natural and artificial intestines used for sausage casings are inedible and must be removed before consumption. Therefore, it has become the practice to peel the sausage casing right at the production plant.
Another technique has been used in sausage making, namely the production of so-called caseless sausages (also designated as skinless sausages), in order to reduce the expense incurred in peeling the sausage casings, the loss of sausage material because the sausages break when the casings are peeled away, and, in addition, the quite sizable cost of the casings themselves.
According to German Patent Publication DE-OS No. 25 23 506, caseless sausages are produced continuously by a machine that is provided with numerous molds, which after removal of the formed and cooked sausage, and after cleaning of the mold, can be used again. One by one these molds pass through a fill station in the machine; a boiling or, as the case may be, a cooking oven; a cooling station; and a mold removal station, whereby between the mold removal station and the following fill station preferably a wash and/or cleaning station is provided. The molds are preferably made of a material having a low coefficient of friction, for instance "tetrafluoroethylene". This designation obviously is to mean "polytetrafluoroethylene". It is, however, in no way indicated that the material used for the molds could be or were required to be pervious for gas.
German Patent Publication DE-OS No. 27 56 995 refers to a process and apparatus for the production of a skinless, chord-like sausage by means of a hull designed as a chord-shaped hollow body which is designated expressly as "practically medium-tight" or "practically medium-tight sealable". The inside of the hollow body may have a smooth anti-sticking layer which, for instance, could be a coating of polytetrafluoroethylene. According to the process described in DE-OS No. 27 56 995, the raw bulk sausage is filled into the casing, then heated, possibly followed by cooling, and finally divided into suitable lengths.
The pressure created during heating due to the expansion of the bulk sausage causes a pressure seal which prevents vapor evolved during cooking to reach the casing exit.
It is also known that a special paper made into an endless tube be impregnated with viscose (a viscous solution of cellulosexanthogenate, which is used for the production of viscose rayon, viscose staple fibers, viscose cellophane and viscose sponges), to form a tubular casing which has a degree of porosity which permits the exchange of moisture and steam. Such viscose impregnated paper tubes can be used for sausages that are to be smoked, because their permeability allows for some penetration of smoke, at least to a degree that exceeds the smoke penetration of most other known sausage casings. Experience has shown that all known multiple reusable but nonporous casings are not suitable for the production of sausage types which must release water vapor, steam and other gaseous constituents. It is, of course, not possible to remove the water vapor, steam and other gaseous constituents from the sausage material before filling.
Also, a previous effort to use a finely perforated sausage wrapper having a large number of holes per square centimeter proved to have severe shortcomings with respect to providing a smooth outer sausage surface, and presented cleaning problems.